Drug May Be New Option to Cut Breast Cancer Risk

June 6, 2011 -- Women over age 60 can safely take an estrogen-lowering drug to reduce their risk of getting breast cancer, a new study shows.

The drug, Aromasin, blocks the production of estrogen that's made outside of the ovaries. It's approved by the FDA to reduce the risk of recurrence in certain postmenopausal women who've already been through at least one bout of breast cancer.

The new study, however, suggests it could also be used to prevent malignancies in healthy women who may have an elevated risk because of age, family history, abnormal breast biopsy results, or other reasons.

The study is published in the New England Journal of Medicine and was presented at the 2011 meeting of the American Society of Clinical Oncologists in Chicago. It shows that Aromasin reduced the risk of invasive breast cancer by 65% compared to a placebo.

In light of the study's findings, researchers say they will give now give women in the study who were unknowingly assigned to the placebo a chance to switch to Aromasin as they continue to be tracked for several more years.

Two other drugs, tamoxifen and raloxifene, which block the effect of estrogen on breast cells, are approved for cancer prevention. But tamoxifen can also have serious side effects, including strokes, blood clots, and endometrial cancers. Raloxifene can have side effects including hot flashes, leg cramps, and joint pain.

Because of the side effects, may women shy away from using those drugs. Research suggests that only about 4% of the 2 million women who could benefit from taking tamoxifen to prevent breast cancer choose to do that.

"A pill that may cause cancer as a secondary effect is a hard sell for healthy women," says study researcher Paul Goss, MD, PhD, a professor of medicine at Harvard University and head of breast cancer research at Massachusetts General Hospital in Boston, who spoke at a news briefing.

Risks vs. Benefits

The study shows that Aromasin, which belongs to a class of medications called aromatase inhibitors, appears to reduce the risk of breast cancer more effectively than tamoxifen or raloxifene and has fewer side effects -- a balance of benefits and risks that many think may change women's minds about the idea of taking a medication in advance of a diagnosis.

"It's a potentially game-changing thing," says study researcher Rowan T. Chlebowski, MD, PhD, chief of medical oncology at the David Geffen School of Medicine at the University of California, Los Angeles.

Researchers who weren't involved in the study agree.

"The study speaks for itself. It is remarkably positive," says Marc E. Lippman, MD, chairman of the department of medicine at the Miller School of Medicine at the University of Miami.

Lippman says it remains to be seen whether women will warm to the idea of taking a medication when they're healthy to lower the chance that they may get cancer later, particularly if it means dealing with side effects.